In an increasingly networked world, more and more traffic, such as data, voice, and video, is transmitted over public and proprietary networks. Wireless networks, in particular, are becoming increasingly popular as networks through which subscribers obtain both voice services (e.g., telephone calls) and data services (e.g., email, web surfing, text messaging, location-based services, etc.).
Wireless networks may support location-based services, in which the location of a mobile device, such as a portable wireless telephone, is used to provide a service to the user. One example of a location-based service is a turn-by-turn navigation service in which directions to a selected destination are provided, based on the current location of the user, as the user navigates to the destination.
A location server may be used to provide location-based services for the mobile device. For example, the mobile device may communicate with the location server to improve the performance of a global positioning system (GPS) unit that is part of the mobile device through Assisted GPS (A-GPS). In A-GPS, GPS information from the GPS unit of the mobile device may be augmented with assistance information from the location server. The assistance information can include, for example, precise orbital information of the GPS satellites, precise time information, information describing local ionospheric conditions or other conditions affecting the GPS signal. In some A-GPS systems, the mobile device may additionally offload some of the GPS calculations to the server. Through A-GPS, more precise location information may be provided to the mobile device than if the mobile device uses only a local GPS unit.
The location server that is to be used by a particular mobile device may change based on factors such as the wireless carrier used by the mobile device or the current configuration of the wireless carrier's network.